Channel Definitions

Satellites (Sats)

The number of satellites.
This is the total number of satellites regardless of the constellations they are in. It will list the total number of satellites the unit is currently tracking by adding the channels GPS satellites and GLONASS satellites. It excludes SBAS satellites and cannot exceed 31.

UTC Time (Time Since Midnight UTC)

UTC is the universal coordinated time, which is accurate to about a nanosecond (billionth of a second) per day.

Position Latitude (48bit)

Latitude is a geographic coordinate that specifies the north-south position of a point on the Earth's surface. Latitude is an angle produced in the GNSS engine using trilateration of satellite time signals from four or more observable satellites. Latitude ranges from 0° at the Equator to 90° (North or South) at the poles.

This will be augmented and ‘lever arm compensated’ using inertial data if an IMU is present and IMU integrated.

Position Longitude (48bit)

Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angle produced in the GNSS engine using trilateration of satellite time signals from four or more observable satellites. Longitude ranges from 0° at the prime meridian to 180° east and west.

This will be augmented and ‘lever arm compensated’ using inertial data if an IMU is present and integrated.

Speed (knots)

Speed is a Doppler-derived channel coming directly from our GNSS engine, this is the 2D speed and has no direction. This data is calculated directly at the reference antenna.

If IMU integration is on, speed will be filtered using a Kalman filter producing a less noisy channel. This is also lever-arm compensated to eliminate the effect of body movement on the roof-mounted measurement location of the GNSS antenna.

Also in the case that the GNSS signal is lost the IMU will continue to provide speed data however this will degrade in accuracy over time.

Heading

Heading is a Doppler-derived channel coming directly from the GNSS engine. This heading will be the ‘course over ground’ bearing at the antenna location with respect to North, irrespective of vehicle direction.  

If IMU integration is on, the Heading value will be filtered using a Kalman filter producing a more noise-free channel that is also lever arm compensated to remove body pitch and roll induced overshoot during high dynamic manoeuvres. If the GNSS signal is lost, the IMU will continue to provide heading data however this will degrade in accuracy over time.

Height (Altitude)

Height is a positional calculated channel using trilateration from four or more observed satellites.

If IMU integration is on, the Height value will be filtered using a Kalman filter producing a less noisy channel. IMU integration will oppose the instantaneous jump in position caused by a satellite signal loss or gain.

Lever arm compensation is also applied to remove the overshoot of position caused by the effect of body movement.

In the case that the GNSS signal is lost the IMU will continue to provide height data, however, this will degrade in accuracy over time.

Vertical Velocity (m/s)

Vertical Velocity is a Doppler-derived channel; it has a direction associated with it (+ve when climbing, -ve when descending).

If IMU integration is on, the Vertical velocity value will be filtered using a Kalman filter producing a less noisy channel. In the case that the GNSS signal is lost, the IMU will continue to provide vertical velocity data, however, this will degrade in accuracy over time.

Lateral Acceleration (G)

This is the Lateral Acceleration (LatAcc) value derived by differentiating the Doppler-derived Speed and Heading channels calculated at the reference antenna.

This measurement is independent of body roll angle.

If IMU integration is on, LatAcc will be filtered using a Kalman filter producing a more noise-free channel, which is also lever arm compensated to remove body pitch-induced overshoot during high dynamic braking or acceleration. In the case that the GNSS signal is lost, the IMU will continue to provide acceleration data, however, this will degrade in accuracy over time.

Longitudinal Acceleration (G)

The Longitudinal Acceleration (LongAcc) value is derived by differentiating the longitudinal component of the Doppler-derived Speed calculated at the reference antenna.

This measurement is independent of the body pitch angle.

If IMU integration is on, LongAcc will be filtered using a Kalman filter producing a more noise-free channel, which is also lever arm compensated to remove body pitch-induced overshoot during high-dynamic braking or acceleration. In the case that the GNSS signal is lost, the IMU will continue to provide acceleration data, however, this will degrade in accuracy over time.

Brake Distance

This is the distance accumulated since the brake trigger was activated.

Note: After the initial trigger activation, any new trigger activations within 2 seconds are ignored. After 2 seconds, if the speed is > 2.7 km/h, the new trigger input will reset the Brake Distance counter.

Distance

This channel is the accumulative total of distance in metres since the start of the file. This channel is calculated via integration of Speed, so is a derivative of a Doppler-derived channel.

Internal Analogue Channels 1-4 (VBOX 3i Products)

The Analogue Channels on VBOX 3i units are user-configurable. The data will be adjusted depending on the scale and offset values set by the user.   

GLONASS Satellites

Lists the total number of GLONASS satellites the unit is currently tracking in the solution. This excludes SBAS satellites.

GPS Satellites

Lists the total number of GPS satellites the unit is currently tracking in the solution. This excludes SBAS satellites.

VBOX Serial Number

This is the serial number of the VBOX unit that is being used. 

Kalman Filter Status

This is the numerical value of the current Kalman Filter (KF) Status. You can look up the definition of your numerical KF value here. 

Solution Type

A numerical representation of the mode of DGNSS correction currently being employed by the GNSS receiver:

0 = None
1 = Standalone
2 = GNSS DGNSS (inc RTCMv2 40 cm)
3 = RTK Float
4 = RTK Fixed
5 = Fixed position
6 = IMU Coast (Kalman Filter)

Velocity Quality

This value is the estimated speed error provided by the GNSS Engine.

Internal Temperature

This is the internal temperature measured in the unit at the current time.  

CF Buffer Size

The current buffer size that is being used for the logging to the CF card. 

RAM Address

Internal use only.

Event Time 1-2

Internal use only.

Battery Voltage 1-2 (VBOX 3i Products)

These are the voltage levels of the 2 internal batteries of the VBOX 3i units.

Position Quality

A numerical position confidence indicator used for RTK robot path following applications.

10 = The difference between GNSS and KF estimated position is better than 5 cm.
9 = The difference between GNSS and KF estimated position is between 5–10 cm.
8 = The difference between GNSS and KF estimated position is between 10 cm and 1 m.
7 = The path following position confidence is between 1–2 m.
2 = When the IMU filter has been enabled and IMU has synced but is not yet initialised. Once initialised it should report as per the above values.
1 = When the IMU has not synced or if the KF has not been enabled (note if KF has not been enabled, then the value will only be present on CAN).

Brake Trigger

The brake trigger is an over-sampled digital input that is used for identifying exactly when the brake pedal is pressed for brake testing or event marking.

True Heading

This is a measurement of the heading from the reference antenna to the secondary antenna with respect to north. When mounted on a vehicle it becomes the measurement of heading that the vehicle is facing.

Slip Angle

The difference between Heading and Slip_Head channels. This is then a measurement of body slip angle at the reference antenna.

As IMU integration affects the heading value, IMU integration will result in a less noisy Slip_Angle channel, it will also translate the measurement from the antenna location to the IMU location.

Note: If the Dual Antenna lock is not valid and IMU integration is not active, there will be no Slip Angle calculations.

Pitch Angle

Pitch Angle is the angle between the two GNSS antennas when configured in “Pitch mode”. This channel gives an accurate measurement of absolute vehicle pitch relative to a zero line. As it is a direct angular measurement, it does not suffer drift over time.

Lateral and Longitudinal Velocity

Lateral Velocity (Knots) The speed of the vehicle with respect to the lateral direction of the vehicle body (90o to the direction of travel): It is derived from GNSS speed and Slip angle; GNSS speed is the speed of the vehicle in the direction of travel of the GNSS antenna.   The VBOX 3i unit's Lateral velocity (Lat_Vel) CAN channel is calculated as follows: Lateral Velocity = Speed x SIN (Slip angle)   Lat and Long Velocity relationship to slip angle: Slip angle = Arctan(Lateral velocity/Longitudinal velocity)

Longitudinal Velocity (Knots) The speed of the vehicle with respect to the longitudinal direction of the vehicle body is derived from GNSS speed and Slip angle; GNSS speed is the speed of the vehicle in the direction of travel of the GNSS antenna.   The VBOX 3i unit's Longitudinal velocity (Long_Vel) CAN channel is calculated as follows: Longitudinal Velocity = Speed x COS (Slip angle)   Lat and Long Velocity relationship to slip angle: Slip angle = Arctan(Lateral velocity/Longitudinal velocity)

Dual Antenna Yaw Rate

This Yaw rate measurement is derived from the rate of change of the True Heading. As such it is noisier than the direct gyro measurement of Yaw rate from the Inertial Measurement Unit.

Roll Angle

Roll Angle is the angle between the two GNSS antennas when configured in 'Roll mode'. This channel gives an accurate measurement of absolute vehicle roll relative to a zero line. As it is a direct angular measurement it does not suffer drift over time.

Slip Angle FL, Slip Angle FR, Slip Angle RL, Slip Angle RR

These channels are body slip angle measurements translated to different locations on the vehicle using yaw rate and X and Y offsets in metres.

Note: If True Heading drops out, no Slip Angle calculations will be made.

True_Head2 (VBOX 3i firmware v2.5 and earlier)

This is a measurement of the heading from the reference antenna to the secondary antenna with respect to north. When mounted on a vehicle it becomes the measurement of heading that the vehicle is facing. When an IMU is connected to the VBOX then this True Heading is combined with the Yaw rate in an online filter to further reduce the amount of noise. This is used in the ADAS vehicle separation calculations.

Note: This channel is only available on a VBOX 3i running firmware v2.5 and below.

Slip Heading (VBOX 3i firmware v2.6-2.8)

When the dual antenna is enabled in a VBOX 3i, this channel is available to log and display as well as transmit via CAN. When an IMU is connected to the VBOX then the true heading measurement is assisted with the IMU-measured yaw rate to reduce the amount of noise of the true heading channel. By using this filtering method, it is suitable for handling and dynamic style testing. Also, if there is an invalid true heading measurement because of an obstruction to the GNSS signal, there is always an accurate measurement of the true heading.
 

The measurement used is dependent on the IMU Integration and Dual Antenna lock status as follows:

Note: This channel is only available on a VBOX 3i running firmware v2.6 and later.

Robot_Head (VBOX 3i post firmware v2.6)

When dual antenna is enabled in a VBOX 3i or a VBOX 3iS is being used, this channel is available to log and display as well as transmit via CAN. It is also used in the ADAS vehicle separation calculations. When an IMU is connected to the VBOX then the true heading measurement is assisted with the IMU measured yaw rate to reduce the amount of noise of the true heading channel. By using this filtering method, it allows vehicles using steering robots for testing to operate in a more stable and gentle manner. Also, if there is an invalid true heading measurement because of an obstruction to the GNSS signal, there is always an accurate measurement of true heading.
 

The measurement used is dependent on the IMU Integration and Dual Antenna lock status as follows:

Note: This channel is only available on a VBOX 3i running firmware v2.6 and above.

Yaw Rate (YAWRate (°/s))

Degrees /second measurement from a gyro in the YAW plane of a vehicle. +ve clockwise.

X-Acceleration (g)

Accelerometer measurement in the vehicle longitudinal plane, +ve for forward acceleration. This measurement is not compensated for gravitational influence.

Y-Acceleration (g)

Accelerometer measurement in the vehicle lateral plane, +ve for acceleration to the left. This measurement is not compensated for gravitational influence.

Z-Acceleration (g)

Accelerometer measurement in the vehicle vertical plane, +ve for upward acceleration. This measurement is not compensated for gravitational influence.

Temp

Value of temperature from the IMU's internal temperature sensor,
NOT ambient temperature measurement.

Pitch Rate (°/s)

Rotational rate measurement from a gyro in the longitudinal axis of a vehicle. -ve nose down.

Roll Rate (°/s)

Rotational rate measurement from a gyro in the lateral axis of a vehicle. +ve for counterclockwise rotation.

DGPS

This channel indicates if the GPS is currently using DGPS correction data to mitigate GPS positional propagation errors. An improvement in the positional accuracy of the VBOX depends on what type of DGPS message is being used.

Elapsed Time

The time elapsed (in seconds) since the start of the file. 

Relative Height

This is an integration of Vertical Velocity performed by the VBOX Test Suite software when a logged file is loaded. It will be zero at the beginning of the file.

This channel has a very high height accuracy over short periods and is resilient to satellites appearing or disappearing.

Radius of Turn

The Radius of Turn channel is derived from the speed and heading channels. As IMU integration affects both of these channels, the radius of turn data will also be smoother when IMU integration is enabled.

The Radius of Turn channel is calculated as follows:

Abs((360 / RateOfChangeOfHeading) * speed / (2 * Math.PI))

Centre Line Deviation

This is a measurement of the vehicle's lateral movement (m). This parameter uses a previously sampled test lane heading as a reference and then from the start of each test creates a lateral deviation measurement. So if the vehicle pulls left during a brake stop then this parameter will display a +ve value in metres.